Proportional control system



Dec. 14, 1943. i i R, MaCKAY 2,336,492

PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 19.38 l5 Sheets-Sheet l MEI/ENT cl/mmvr Flaw M07' l? 17 $91-120 je@ J. R. MacKAY 2,336,492

PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 1938 l5 Sheets-Sheet 2 Dec. 14, 1943. .1 R. MacKAY 2,336,492

PROPORTIONAL CONTROL SYSTEM Original Filed Deo. 5, 1938 l5 Sheets-Sheet 3 Dec. 14, 1943. 1. R. MacKAY 2,336,492

PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 1938 l5 Sheets-Sheet 4 Dec. 14, 1943. J. R. MacKAY 2,336,492

PRoPoRTIoNAL CONTROL sYsTEM Original Filed Dec. 5, 1938 l5 Sheets-Sheet 5 Dec. 14, 1943. J. R. MacKAY PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 1938 l5 Sheets-Sheet 6 wnN NMN funk .Ik

Dec. 14, 1943. J. R. MacKAY PRoPoRTIoNAL CONTROL SYSTEM Original Filed DeG. 5, 1938 15 Sheets-Sheet 7 ,MM am www. www, Sd,

Dec. 14, 1943. J. R. MaCKAY PROPORTIONAL CONTROL SYSTEM 15 sheets-sheet s Original Filed Deo. 5. 1938 QNMN n. NMM

J. R. MaCKAY PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 1938 l5 Sheets-Sheet 9 Dec. 14, 1943. .1 R. MacKAY PROPORTIONAL CONTROL SYSTEM 1938 l5 Sheets-Sheet l0 Original Filed Dec. 5

aww

Dec. 14, 1943. J. R. MaCKAY 2,336,492

PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 1938 l5 Sheets-Sheet ll MSM..

QQ Nw Q m ww mw @wwwa un gagna/1 may i i l I Dec. 14, 1943.

PROPORTIONAL CONTROL SYSTEM J. R. MaCKAY 15 "sheets-sheet 12 rfCf/z/E/ 5 UMA/5114177E/` 1 2 0 4 5 0 7' 0 0110100 .s1/v 0 1001/1 F1011/ 11000 000107 .s1/v7' g1g x. 0572 90 1.00000 0 0 0 0 0 0 55 .99.939 .00061 .l .l .048 .00011352 .000597 F00 .99750 .00244 .0 .04 .192 .00224 .002402 04 .99452 .00540 1.2 1.44 .422 .007500 .005400 Z ,99027 ,00970 1.0 2.50 ,700 .0104002 0095 75 210 ,90401 .01519 2.0 4.0 1.2 .02094 .014959 70 .97015 .02105 2.4 5.70 1.720 .0001572 .021544 70 .9705 ,0297 2.0 7.04 2.052 .0410040 ,029015 74 .90120 .07074 2.2 10.24 0.072 .0505920 .000 20 72 .95/00 .04094 5.0 12.90 0.000 .0070112 .04044 70 .90909 .00021 4.0 10.0 4.0 ,00000 .059 70 00 .92710 .07202 4.1 19.20 5.000 .1011992 .07229 00 ,91255 ,00040 4.0 20. 04 0. 912 .1200010 000179 04 .09079 .10121 5.2 27: 04 0.112 .1411000 .100000 02 .00295 .11 705 5.0 01,00 9 400 .1004041 1 1 0 770 0 0 .00000 ET1557 0.0 00. 10.0 .10770 1000 04 50 .04005 W.7175195 0.4 40.90 12.200 .2120204 15204 50 *102904 .17090 *0.0m A40.24 *10.7072- E11-000n ".110772-4A h54H*009-0.;'f1-4090 n 7.2 51.04 15.552 .2001170 .19154 T .70001 .21199 7.0 07.70 17.020 .2970404 .21277 5 0 k70004 .20090 0.0 04. 19. 2 .02007 20494 40 7491; m*.125000" 0. 4 70.50 21.100 .5011010 257909 46 71904 l.20000 ,0.0 77.44 20.2 02 .0944504 .20100 44 0010-0`-00`524d 9.2 04.04 25.592 l1200101 .00004 42 *u* 00910 '7.55007 9.0m 92.10 27.010 .4040000 .001500 40 64279 .55721 10.0 100.0 30. 0 .50000 35720 m W (RW-KM -l M C. W12/VL mmv Dec. 14, J. R. MacKAY PROPORTIONAL CONTROL SYSTEM Original Filed Dec. 5, 1958 l5 Sheets-Sheet 13 Dec. 14, 1943. J. R. MacKAY 2,336,492

PROPORT IONAL CONTROL SYSTEM Original Filed Dec. 5, 1938 15 Sheets-Sheet 14 1 2 6 4 5 6 7 M015 R .5l/v l? F/.0W 11500 fl/vLf- `S//V T '-smf/Z 90 1 0 0 ..25 .42262 1.00000 68 @99969 .4 .16 24.96 .42196 .999446 66 .99756 .6 .64 24.64 .42011 .997666 64 .99452 1.2 1.44 24.64 .41691 .995166 62 .99027 1.6 2.66 24.66 .41246 .99140 60 .98461 2.0 4.0 24.0 .4067 .96656 78 .97815 2.4 5.76 26.56 .69997 .980345 76 .9705 2.6 7.04 25.04 .69137 .97.557 74 .96126 6.2 10.24 22.44 .66169 .96569 72 .95 1 06 6.6 1 2. 96 21.76 .670 72 .95611 70 .96969 4.0 16.0 21.0 .6.5667 .94566 66 .92716 4.4 19.66 20.16 .64464 .964 07 66 .91355 4.6 25.04 19.24 .52956 .92129 64 .696 79 6.2 27.04 15.24 .61600 .907626 62 .66295 6.6 61.66 17.17 .29626 .69260 60 .66606 6.0 66.0 16.0 .27664 .67574 58 .64605 6-9 40.96 14.76 .254 77 .656106 66 .62904 6.6 4 6.24 y16. 44 .26246 .669 22 54 .60902 7.2 61.64 12.04 .20660 .619076 mln 'Ka-rk,... RMM K Dec. 14, 1943. J. R. MacKAY PROPORTIONAL CONTROL SYSTEM Patented Dec. 14, 1943 PROPORTIONAL CONTROL SYSTEM John R. MacKay, West Caldwell, N. J., assigner to Wallace & Tiernan Products, Inc;, Belleville, N. J., a corporation of New Jersey Original application December 5, 1938, Serial No.

244,054. Divided and this application December 26, 1939, Serial No. 311,035

claims. (ci. 17a-zas) This invention relates to proportional control systems and procedure, particularly of the electrical type, whereby one or more elements or quantities are to be controlled in proportion to variations of one or more master elements or quantities. An important object of the invention is to provide a new and improved system including transmitting and receiving stations, wherein the control at the receiving station may be exercised continuously and with practically instantaneous response to changes at the transmitting station, and wherein the principal control circuit is substantially free of current flow at all times, so as to prevent reaction back from a controlled to a controlling instrument, and so as to cooperate in the attainment of a number of other objects and advantages hereinafter apparent, or incidental to practical applications of the invention. Another important object is to provide improved electrically operated control systems which are readily adapted to a wide variety of metering, telemetering, and remote control purposes; and to provide systems of the character described, which are substantially unaffected by changes in temperature, power line voltage, and the like.

Further objects of the invention are to provide electrical control systems for operating chemical feeders, chlorinators, recorders and like devices in proportion to the iiow of a iiuid such as water or sewage, or 'other substance being handled or treated, and/or in proportion to chemical or other properties of the fluid or other substance, wherein greater accuracy, sensitivity and reliability are obtained than in prior systems; wherein there is less frictional or other load on delicate controlling or controlled devices; wherein there may be no necessity for the use of synchronous motors or other synchronizing devices at both the transmitting and the receiving points, such as required in some prior systems; and wherein there may be included a variety of special, multiple or composite features of control, which are unobtainable or unsatisfactory in systems heretofore available.

Other objects are to provide new and improved instrumentalities and combinations thereof, in and for systems of the character described, including arrangements for readily matching a receiving device to a specific transmitting condition; for effecting secondary proportioning or dosage control-e. g., in proportionally controlled feeding devices, varying the amount of substance fed per unit quantity of treated material; for effecting simiar secondary control according to an automaticprogram, or automatically in proportion to other variables as well as in proportion tothe master or principal variable, or automatically to decrease the rate of receiver response (whereby fluctuation or hunting is minimized, when it might otherwise exist); for efflciently interrelating a plurality of controlled or controlling devices or both (while separately effecting various secondary controls, as desired); and for producing, in a simple manner and without the use of cams or like compensating devices, a linear or substantially linear response to a nonlinear control variable such as a control meter operating in proportion to the square of the quantity primarily concerned.

Other objects and advantages of the invention, relative to procedure and apparatus whereby greater simplicity. economy and emciency may be obtained in proportional control apparatus, and whereby various further controls of special advantage may be afforded will be hereinafter stated or apparent in connection with` the following description and accompanying illustration of certain presently preferred embodiments of the invention, set forth by way of example.

In the drawings, which are Wiring diagrams of control systems unless otherwise noted: Y

Fig. 1 shows a proportional control system for operating an indicator from a now-responsive transmitter;

Fig. 2 is a plan view of an inductor suitable fo use in the systems of the invention' Fig. 3 is a section on line 3-3 of Fig. 2;

Fig. 4 is an elevation, partly broken away, of the inductor of Figs. 2 and 3;

Fig. 4-A is a side view, partly in section, of the rotor of the device in Fig. 3; Fig. 4B showing an alternative rotor:

Figs. 5 and 6 are respectively elevation and perspective views of another structurev of inductor;

Fig. 7 is a modification of the system of Fig. 1, including secondary proportioning means;

Fig. 8 is a further modified proportional control system, including a plurality of controlled devices;

Fig. 9 is another modified system, with selectable controlling and controlled devices and a modified structure of such devices;

Fig. 10 is another modification including a plurality of transmitters exercising joint control;

Fig. l1 shows a modication of certain simplified connections illustrated in Fig. 10;

Fig. 12 is another system providing for an au- Vtends to certain receiving tomatic program of secondary proportioning or dosage control;

Fig. 13 is another system for controlling a, chemical feeder automatically in accordance with both the flow and chemical nature of the treated material;

Fig. 14 is a modification of certain controlling arrangements in Fig. 13;

Fig. 15 is a further system wherein a single amplifier is used for a plurality of controlled devices, and wherein the rate of response of a controlled device can be slowed down as desired;

Fig. 16 is another system. wherein the ilowresponsive control of a feeder is checked against the rate of feed of the latter;

Fig. 17 is a modied system for producing a linear response to a non-linear control;

Figs. 17--A to D inclusive are sections of control instruments used in Fig. 17, in various positions;

Fig. 17-E is a graphic representation of the operation of the devices shown in Figs. 17 to 17-D;

Fig. 17-F is a table indicating the relation of various numerical `quantities entering into the operation of the devices shown in Figs. 17 to 17-D;

Figs. 18, and 18-A to F inclusive respectively correspond to Figs. 17 and 17-A to F inclusive, and similarly illustrate a modification of the arrangements illustrated in the last-mentioned figures;

Fig. 18-G is a fragmentary view showing a further modification of part of the circuit shown in Fig. 18; and

Fig. 19 is a graphic representation of the operation of systems such as illustrated in Fig. 7, under certain conditions.

Attention is first directed to Fig. 1 of the drawings, which illustrates certain important features of the invention, relating to systems for automatic proportioning and control. A flow type of transmitter generally designated I is arranged for response to the vertical movement of the liquid in a iioat chamber 2. Such chamber may, for example, be a weir box of well known construction, wherein the movement of a oat 3 bears a definite exponential relation to the flow of liquid through a notch or orifice on the weir. Vertical movement of the float 3, facilitated by its counterweight 4, causes rotation of the pulley 5, to the shaft of which, and through the medium of suitable gears or other coupling means, is attached the rotor 6 of the inductor 1; the rotor being suitably journaled for rotation with respect to its stator winding 8.

The circuit of the transmitting inductor 'I exinstrumentalities, among which there is diagrammatically shown a relatively simple indicating device I0, comprising a shaded pole motor 9 which has its rotor 9a geared to or otherwise arranged to drive an indicator pointer II traversing a scale Ila. The pointer II is itself geared or otherwise arranged to rotate positively a cam I5 which in turn, by means of the follower arm I5a, revolves the rotor I2 of a receiving inductor I3, relative to the stator winding I4 of the latter. The cam I5 is provided so that it may convert the movement of the float 3, which is non-linear with respect to the rate of flow of the liquid, into a substantially uniform or linear movement of the pointer II, in the course of operation of the apparatus as hereinafter described.

An ampliiier I6 which may comprise one or more voltage amplifier stages followed by a power amplifier stage is provided for energization of the opposed shading coils I1, I1, of the motor 9. Suitable ampliiiers of the type mentioned are well known, and thus for convenience of illustration, in this and other figures, the amplifier is simply indicated with a representation of a single vacuum tube and transformer. For like reason, a simplified representation of a shading coil motor, as at 9, has been employed in the several drawings, omitting the core and showing only two shading coils, instead of four or more as would preferably be employed.

Suitable amplifier-controlled shading coil motor apparatus of this type is described in my copending application Serial No. 74,895, filed April 17, 1936 for Motor control apparatus, to which reference may be had for a full description of such apparatus. In brief, the motor 9 has a field winding I8 connected across an alternating current line 22, and has a plurality of shading coils I'I, each of which is wound with a multiplicity of turns. The shading coils are normally opposed in electrical eect, so as to keep the rotor 9a stationary when no external current is applied to them, but they are so connected (advantageously in series) to the secondary of the output transformer of amplifier I6, that in accordance with the phase relationship between the alternating current in the amplier output and that from the line 22, the electromotive forces normally induced in one shading coil (or set of coils, if more than two coils I'I are used) are assisted and the electromotive forces normally induced in the other shading coil (or set of coils) are opposed and preferably overcome, by the electromotive force set up in the amplifier output, whereby rotation of the rotor is produced in one direction or the other depending on the phase relation between the current from line 22 and that from the amplifier output. The existence and phase relation of an alternating voltage at the amplifier output are dependent upon the existence and phase relation of such voltage across the amplifier input; and as will be apparent from the description of the other apparatus, the latter voltage, when it appears, will be approximately in phase or out of phase with the voltage of line 22, so that the motor 9 will be caused to operate in one direction or the other.

Although I at present generally prefer to use motor apparatus of the type described in the aforesaid application Serial No. 74,895, since it requires little amplifier output for its positive operation, is essentially non-hunting, and is extremely sensitive to changes of voltage and phase, other types of motors or actuating devices may be satisfactorily used-for example, instrumentalities similar to the amplifier-controlled galvanometer apparatus employed to operate a potentiometric device in Figs. 14 and 15 of my copending application Serial No., 210,984, iiled May 31, 1938, for Voltmeter apparatus.

The rotor windings 6 and I2 of the transmitting and receiving inductors 'I and I3 respectively are preferably connected in series'with the input of the amplifier I6, as shown, so that alternating electromotive force will only be impressed on the input of the amplifier when the voltages produced by the opposed windings B and I2 are unequal.

In the specific example of Fig. 1, the series connection through the receiving rotor I2 is effected across a potentiometer I2a for purposes hereinafter explained, but for simplicity of description it may be temporarily assumed that the potentiometer is omitted and the amplifier input lead I2b connected directlyvto the upper side 0f the rotor winding I2. I

The stator windings 8 and I3 of the respective inductors are conveniently connected for energization from the alternating current line 22, and are preferably connected in series opposition, as by means of conductors I9, 20 and 2 I, in the manner illustrated in Fig. l. By virtue of this arrangement fluctuations in line voltage will affect both inductors in a similar manner and automatic compensation will also be afforded for differences in temperature between the locations of the receiving and transmitting instrumentalities, since any change in the resistance of the copper stator windings due to temperature will result in a change in the current through both of the inductor stators and will. thus produce no change in their ampere-turn relationship. This feature is of particular value in water works installations and the like, where the temperature of the transmitter will usually follow variations in climatic and water temperatures, while the receiving apparatus will usually be located in a protected and heated structure and thus have a relatively stable and constant temperature.

From the preceding description it will now be appreciated that if suitable alternating current is applied to the line terminals 22 a voltage will be produced in the rotor windings G and I2. If these windings and the windings 8 and I3 of their respective stators 'are alike, the voltages will be equal in value and opposite in phase, providing the angular positions of the rotors are similar; and no electrornotive force will then be impressed on the input of the vacuum tube amplifier I6. If, however, the angular position of one rotor should dilTer from that of the other, an alternating E, M. F, of an amplitude proportional to the extent of the difference. and of phase corresponding to the direction of the diierence, will be impressed on the input to the amplifier I6, whereby the amplier will effect energization of the shading coils i 'I of the motor 9 and operate the motor, in such a manner as to restore balance between the inductors. When the receiver rotor I2 has thus been moved to the new position of balance with transmitter rotor 6, the motor will again come to rest.

A It will now be seen that the described apparatus provides not only a simple and reliable proportional movement system but also a system that is fully compensated for both voltage and temperature. Of special importance, moreover, is the fact that no appreciable reaction is produced on the transmitter I by the receiving rotor i6, since the rotors 6 and I2 are connected in series with the grid circuit of the rst voltage amplifier stage of amplifier I6, and since that amplifier stage may preferably be operated with suilcient C bias (e. g., negative grid bias) to prevent any ilow of grid current at any time. so that no current ows in the windings 6 and I2 at any time and no electromagnetic reaction can result. Furthermore, since there is preferably never any flow of current in these windings, any variation in their resistance, due to temperature changes, has no effect on their voltage.

Although in a number of cases the system may' be used without such means, the inclusion of the potentiometer I2a in the circuit across the receiving rotor I2, makes it possible to increase or decrease the amount of angular movement oi rotor I2 and associated pointer II which will correspond to any given amount of rotation of the Y transmitter inductor rotor 6. It may be explained that it is often impractical, from a mechanical and commercial standpoint, to design and -construct a recorder which will exactly match a particular transmitter condition--for example, because the parts haa/e to be standardized for manufacture in quantity, or because eld data concerning flow, pressures, and the like are often inaccurate by reason of a lack of suitable facilities for their close determination. In such cases, the illustrated circuit is of special advantage. in that the potentiometer I2a spreads or contracts the range of response of the receiving apparatus and allows the receiver to be accurately matched to the transmitter at the time of installation.

Thus, for example, if the voltage output of the transmitter rotor 6 is 30 volts when it has been moved to a predetermined position, which for 'purposes of illustration may be taken as a deflection of 30 from Zero position, and which may correspond, say, to the Imaximum flow position of the float 3, it will be necessary for the rotor I2 to turn through a greater angle in order to produce the same voltage between one side and the center arm of the potentiometer I2a, so that balance can be established and the motor 9 brought to rest in the manner previously explained. Tha-t is, other things being equal, the rotors 6 and I2 being themselves identical in actual voltage output for the same relativefpositions, and the potentiometer arm being set at a selected intermediate point, the receiver rotor I2 will not stop at the same angle as the transmitter, but must move to a greater angular position (i. e., a position of closer inductive coupling since only-such part of the receiving rotor voltage as is proportioned by the potentiometer I2a is applied in opposition to the voltage generated by the transmitting rotor 6.

Hence it will be seen that the range of movement of the indicator arm II can be ampliiied or spread, by moving the arm o-f the potentiometer I 2a in a clockwise direction (as viewed in the drawing). In most instances o1' the system shown, moreover, the transmitting and receiving inductors are preferably so wound or otherwise constructed or arranged relative to each other, that the voltage of the transmitting inductor rotor at its highest available angular position is somewhat less than that of the receiving inductor rotor for the same angular position, so that the range of the indicator arm II can be either increased or decreased, by adjustment of the potentionmeter arm one way or the other from a determinable position of voltage equality. This basic voltage relation of the inductor rotors is indicated, for example, in Figs. 1 and 7 (hereinafter described) by a larger number of turns on the receiving rotor than on the transmitting rotor.

For best results in many cases where a resistance such as potentiometer I2a is connected across the receiver rotor I2, a corresponding resistance such as the xed resistor 6a may be connected across the transmitter rotor 6, to obtain optimum phase relationship between the inductors.

It will be understood that although the motor 9 is shown connected to drive an indicator pointer, it may in addition or instead be arranged to operate or control one or more other devices, such as recorders, liquid or dry chemical feeders, or the like, and that although the transmitting inductor is controlled by a flow-responsive float, it may be operated by other devices responsive to the variation of a quantity for which proportional control is desired; the same being generally true of other systems o1 the invention hereinafter described. y

Figs. 2, 3, 4 and 4-A illustrate a satisfactory form of inductor for use in the circuit of Fig. 1 and in other circuits hereinafter described. In this inductor structure, the stator winding 8 is supported on a split form .23Y of insulating material such, for instance, as molded Bakelite. By making the stator in two sections the rotor can be installed with only the slightest dismantling of the associated parts. A wire 24 connects the two stator halves in series so that they are in electrical effect a single winding, as represented in Fig. 1; terminals 25 and 26 being provided for making connections to the ends of the winding.

'The rotor winding 6 is supported on a ringshaped core 21, preferably of insulating material, and is conveniently contained in an annular groove 28 molded or machined in the core. A ring of insulating material 29, concentric with the core and closely fitting it, is pressed in place around and over the rotor winding, as shown, so as to provide both a protection for the latter and a means for the support of the shaft 30 and the pivot 3|. Glyptol lacquer, or like sealing material, may be used for impregnation of the windings 6 and 8 and for the production of a moisture tight seal between the rim,T 29 and the core 21.

The shaft 30 and pivot 3|, for supporting the rotor are conveniently pressed into insert members 32, which are molded or screwed in the Bakelite ring 29 so that a strong and secure an-4 chorage is obtained. Respectively adjacent the inserts 32, small holes 32 and 3| are provided in the ring 29, and the ends of the winding 6 extend out through the holes and are soldered to the inserts, respectively, so that electrical connection to the Winding can be made through the shaft 30 and pivot 3|.

The end of the shaft 30 seats against a pivot bearing 33 of hardened conducting material, such as heat treated beryllium copper, which is carried by a metal arm 34 supported on the insulated stator form 23 by the bushings or studs 35. This provides both a well insulated bearing and at the same time acts as a terminal for attaching a connecting lwire 36.

The pivot 3| is seated in a thrust bearing 31 of heat treated beryllium copper (or like material) which is urged against the pivot by the coil spring 38, as shown. The bearing and spring are housed in a metal container 39 which is clamped in position between the two halves of the stator forms 23. A retaining screw 40 keeps the spring 38 under compression and also has a tubular I recess 40a in which a pin 31a, comprising an extension of bearing 31, is slidably guided. The screw 40 provides a means for attachment of the connecting wire 4|.

A collar 42 is pressed on the shaft 30 and serves as a support for the drive gear 43 which is preferably made from Bakelite or other insulating material. The gear 43 is forced into frictional Contact with the collar 42` by the friction spring or spider 44, so that the gear can be used to rotate the shaft 30 and the rotor assembly. A nut 45 retains the spring 44 in engagement with the gear, which otherwise would be free to rotate on the collar 42 abcut the axis of the shaft 36. It will be understood that thefrictional connection of the gear 43 is such that the rotor may be displaced or adjusted 'relative to the gear-for example, by manually turning the core 21 while holding the gear.

In order to prevent the induction of electromotive forces in the rotor by magnetic fields which are produced by motors or other equipment often associated with the inductor devices, a cylindrical shield 46 of ferrous material is placed completely around the inductor assembly, coaxially with the shaft 30. Particularly in instances where the inductor may be mounted in a recorder case or other container: made from a ferrous material and where relative movement between the inductor and casing structure may occasionally take place (as upon opening the case to take readings or to inspect or adjust other devices), it is often desirable to enclose the ends of the cylindrical shield 46 withend plates (not shown), likewise of iron or other ferrous material. Such construction eliminates errors due to induction or to the increase and decrease of inductance that would otherwise exist when the distance between the inductor device and the iron recorder or motor casing is varied.

Ordinarily air-core inductors (i. e., having a core of air or other non-magnetic material) are at present preferred, as aording maximum accuracy and uniformity of response; and Fig. 4-B illustrates a rotor suitable for use in the .inductor of Figs. 2, 3 and 4 (instead of the rotor actually shown in Figs. 3 and 4-A) so as to constitute an air-cored device. However in certain cases, the rotor may be as shown in Figs. 3 and 4-A, wherein the rotor winding support 21 has a large central opening into which a soft iron ball 41 is cemented or otherwise fastened, with its .center on the axis of shaft 3D and pivot 3|. This spheri- ,cal ball constitutes an iron core and as a result j' a greater number of magnetic lines of force traverse the winding 6, which in turn produces an increased voltage output and has a greater sensitivity to angular movement.

Since in many instances the angular position that the rotor will be required to assume will be different from that of the rotor in the controlled or receiving unit (for example, where secondary proportioning is employed, as in systems hereinafter described), it is extremely desirable that there be no appreciable phase shift other than a shift of at any time, and that apart from a phase shift of 180, there be merely a change in the magnitude of the two voltages. That is, for instance, if the entire rotor core 21 were made from iron or other magnetic material having an annular groove cut into it to receive the rotor winding, the non-symmetrical shape of the core would occasion considerable phase shift as the rotor is turned. However, by using the spherical core 41 (or by the use of an air core) the relation between the stator winding and the core remains constant for all positions of the rotor and no shift in phase occurs to reduce the sensitivity of the inductor to small angular changes.

Figs. 5 and 6 illustrate an alternative inductor construction which is highly eicient, which also does not appreciably change its phase angle as it moves through an arc of 180, and which is especially adaptable to long distance transmission where line voltage losses should preferably be kept down, as by the use oflow current devices.

The device of Figs. 5 and'6 includes a field core structure 48 of laminated iron or steel, which is magnetically energized by the stator winding 49, as shown. A rotor winding 53 wound on a light metal or Bakelite form has outwardly-extending supporting shafts or pins 58 which are journaled in the bearings 50a, the latter being mounted on the insulating strips 8| which may also serve as a mounting for terminal lugs 82; for simplicity, the drawings show only one shaft 50, bearing 50a and strip 31,1. e., only one side of the device. It will be understood that the axis of coil 53 is perpendicular to and passes through the axis of its shafts 80, and that coiled flexible leads M are provided to make connection with the windins 53.

A further stationary core or center section 55, also of laminated iron or steel, is located centrally in the circular opening 56 of the stator core 48, and is there supported bythe non-magnetic clips 81. As this central core is cylindrical in shape, symmetrical, and coaxial with the shafts 50 of the rotor, there is no appreciable phase shift when the angular position of the rotor winding 53 is varied.

Figure 7 shows a system generally similar to Fig. l, but including additional elements in combination, to provide for the manual secondary proportioning of a quantity which is also maintained automatically proportional to a, master quantity.

Referring to Figure 7, it will be seen that the transmitting inductor rotor 65 is movable through a predetermined arc, say 30, by the action of the follower arm 68 on a cam 81, which in turn is driven by the iioat 88 as it rises and falls with the movement of the liquid 89 in the Weir box 10. The cam 81 may conveniently be of such contour as to convert thev exponential movement of oat 68 to a uniform'angular movement of the rotor 85; inrother words, so as to cause a movement of theinductor rotor suitable for producing voltage increments thatv are linear and correspond directly to the actual flow of the liquid 69 through the notch of the weir.

As in Fig. 1, an amplifier 1I is connected to supply energy to the opposed shading coils of the motor 12. A variable speed drive mechanism or gear box 13 (which can be of known construc- K tion) is arranged to be continuously driven by a separate electric motor 14. At the opposite end of the gear box is its variable speed output shaft 15, which, by means of the belt 16, drives the apparatus (not shown) for which proportional control is desired, e. g., chlorine feeding apparatus, a dry chemical feeder, or the like. A Worm 11 and a worm gear 18 control the output speed of the variable speed drive mechanism 13, and are rotated by the reversible motor 12. Geared or otherwise connected to the same shaft as the worm 11 (or the gear 18) is the receiving inductor rotor 19, which is so wired (just as in Fig. l) that its E. M. F. is opposite in phase to that of the transmitting inductor rotor 85.

From the foregoing and from the explanation of preceding gures, it will be seen that if the transmitting rotor 65 is displaced, the resulting unbalance will cause an E. M. F. to be applied to the input of the amplifier 1|, which in turn will energize the shaded pole windings of the motor 12 and cause the receiving rotor 19 to be positioned at a point where its voltage, as proportioned by the spread potentiometer 80, is equal and opposite to that of the transmitter rotor, or some predetermined proportion thereof. At the same time, by virtue of the worm 11 and worm gear 18, the same operation of motor 12 causes the variable speed box 13 to vary the speed of its output shaft 15 in proportion to the change in flow of liquid as indicated by the extent and character of the voltage unbalance produced by the precedent displacement of the inductor rotor 85 at the Weir box transmitter.

As explained in connection with Figure 1, the spread control potentiometer 80 permits matching the range of the variable speed drive (e. g., the receiving instrumentalities) to transmitter conditions. In Fig. 7, another potentiometer 8|, with a calibrated dial 82, is connected across the circuit of the transmitting inductor 85, and so connected, serves the further and very valuable purpose of secondary proportioning or dosage control.

For example, let it be assumed that the belt 18 is arranged to drive a dry chemical feeding device `(not shown) for treating a liquid in proportion to the rate of ow of the liquid as determined by the float 68 in the weir box. In many cases the amount of treating chemical required, say, per million gallons of the liquid being treated may be more or less at some times than at other timesfor instance, where the need of the liquid for treatment varies with the time of day or the season of the year-yet of course the chemical feed must always be proportioned to the rate of flow of the liquid. The secondary proportioning or dosage control can be accomplished with the arrangement of Fig. 7 and without interrupting the general continuance of proportionality to rate of flow, since by the potentiometer ldevice 8l, 82, the effective voltage from the transmitting inductor rotor 65 is reduced to any proportional fraction thereof (from 100% to zero) in accordance with the setting of the readily calibrated dial 82 and the associatedpotentiometer arm. That is, by turning the dial 82 one way or the other, the reagent feeding apparatus (under control of the receiving instrumentalities) will be made to increase or decrease its rate of feed just as if there had been an increase or decrease,

respectively, in the rate of flow of the liquid under treatment; while subsequent actual changes in the rate of flow will effect proportional change in the feeding of reagent as previously explained, at a rate of change determined by the setting of the potentiometer device 8i-82.

Figure 7 thus illustrates a system for the automatic proportional control of a second quantity by a master or first quantity, with provisions for matching the receiving or controlling equipment to any particular transmitter condition or range, and for secondarily proportioning the transmitter output to permit dosage control.

In this and'other illustrated embodiments of the invention, each of the various resistance devices, such as the spread and dosage control potentiometers in Fig. 7 or the spread potentiometer 12a and resistor 6a in Fig. 1, is preferably of very high resistance-for example, of the order of 200,000 ohms Where the rotor output is of the order of 30 volts-and thereforeabsorbs such a small amount of energy from the inductor rotor as to cause substantially no electromagnetic reaction between the rotor and its stator. As previously explained, the amplifier input preferably draws no current from the rotors; on the other hand, potentiometer resistors connected across them necessarily draw some current but if the resistance value is high, the flow of current is kept to such a small amount that no.

measurable reaction occurs-the effect being that of no current flow, and the condition is therefore conveniently so defined elsewhere herein and in the appended claims. 

